\documentclass[11pt]{article}

\title{Title}
% \subtitle{Subtitle}
\date{\today}
\author{Kyle Butts}
% \institue{}

\input{preamble.tex}

\makeatletter
\newcommand\primitiveinput[1]
{\@@input #1 }
\makeatother

\begin{document}

\begin{table}[tp]
    \caption{Effect of Treatment on Prices}    

    \begin{adjustbox}{center}
        \begin{tabularx}{\textwidth}{@{}
                LCC
            @{}} 
            % Head
            \hline \hline
            & \multicolumn{2}{c}{\textit{Dependent variable:} \ Prices} \\ 
            \cline{2-3} 
            & (1) & (2) \\
            \hline

            % Body ----------
            \primitiveinput{table1.tex}
            \hline 
            
            % Notes ----------
            \multicolumn{3}{@{} p{\textwidth} @{}}{\small\textit{Notes:} This is where authors provide additional information about the data, including whatever notes are needed.}
        \end{tabularx}  
    \end{adjustbox}

\end{table} 


\end{document}